This invention relates generally to oil well equipment utilizing as a part thereof resilient, at least partially flowable, rubber or elastomeric material for maintaining a continuous pressure seal against a well element, such as drilling pipe, or for maintaining closure under well pressure conditions of a well casing such as in blowout preventers. The utility of the invention is not limited to the above examples or to oil well equipment.
In one example in oil drilling equipment, a continuous seal is often provided around drill pipe while the pipe is moved vertically or axially. Under such operations the sealing face of the rubber material may be ripped, torn and gouged by irregularities in the drill pipe surface and by the slightly larger diameter drill collars connecting pipe sections. Thus, under such conditions, while the resiliency of the rubber may continue to exert a sealing pressure on the drill pipe surface; however, the rubber sealing surface may become irregular and worn and the seal member must be replaced.
Blowout preventers are employed to tightly grab a drilling string or pipe under pressure to seal off the well against well fluid pressures. When the resilient face of the blowout preventer sealing rubber member is tightly pressed against a pipe for a period of time and when the blowout preventer is actuated to release position, the tight pressure contact of the sealing face of the rubber against the pipe often tends to create a suction at the sealing interfaces which sometimes tends to separate small particles of the rubber sealing face from the rubber body and thus destroy the effectiveness of the seal when the preventer is again actuated.
Such a condition may also exist when a pair of rubber rams are used to seal off the well casing when the drill pipe has been removed and the gatelike ram assemblies are urged into tight pressure contact to maintain such seal against fluid pressures developing in the well. To contain such fluid pressures, preferably the sealing faces of the ram rubbers should properly mate or interface to maintain the desired sealed shutoff.
While the material of the ram rubbers is compounded to maintain a selected standard of resiliency, yieldability and resistance to well fluids, a need was recognized for reinforcing the rubber material against the stresses imparted thereto. One prior proposed seal means for drilling heads involving a rubber stripper provided a plurality of longitudinally extending annularly spaced rods or wires of steel molded in the rubber body of stripper. Such rods provided longitudinal strength for a stripper rubber sealing element, minimized longitudinal compression of the sealing element and reinforced the rubber material of the sealing element to provide a continuous seal (See U.S. Pat. No. 3,029,083).
In another prior proposed seal means a helical spring in the form a ring-like washer was molded and embedded in the rubber material to provide reinforced resilient expansion of the stripper body while a drill collar on a drill string moved past the stripper. (See U.S. Pat. No. 2,179,915).
Reinforcement of ram rubbers to strengthen the rubber body member by using layers of suitable fabric embedded in the rubber body in spaced relation to the sealing face has also been used. (See FIG. 17 of Shaffer Tool Works Catalog, 1960, page 4939.)
Prior proposed reinforcements of rubber materials used for sealing devices in oil well equipment were of assistance but did not fully meet field requirements of durability, reliability, long life, and constant protection against the various types of fluids encountered in a well drilling operation.